(The Root) -- After calling nearly three dozen witnesses over nine days leading up to the dramatic moment when Trayvon Martin's mother took the stand, the prosecution on Friday rested its second-degree-murder case against George Zimmerman.

Did the state prove Zimmerman's guilt beyond a reasonable doubt? That seems as improbable as parts of his account of fatally shooting the Florida teen in self-defense.

Prosecutors held the most highly anticipated testimony until Friday, hoping Trayvon's mother and brother and the results of his autopsy would deliver a powerful final impact for the jury. Sybrina Fulton's compelling comments about her son got the state off to a solid start, but the uneven, at times odd testimony of a medical examiner seemed to bring the prosecution's case to a sputtering end.

Fulton on the stand marked the emotional peak of the trial. As she listed her children by name, she came to her youngest: "Trayvon Benjamin Martin. He's in heaven." She described his tattoos: praying hands on a shoulder with the names of his grandmother and great-grandmother, her own name on his left wrist.

Assistant State Prosecutor Bernie de le Rionda played the 911 call from the night of the shooting that includes screams of help in the background.

"Ma'am, that screaming or yelling, do you recognize that?" de la Rionda said.

"Yes," Fulton said. "Trayvon Benjamin Martin."

On cross-examination, defense attorney Mark O'Mara asked Fulton, "If it was your son screaming, as you testified, then it was George Zimmerman who caused your son's death?"

"Correct," she said.

If it was Zimmerman's screaming, O'Mara asked, would it mean that Trayvon was responsible for his own death?

Fulton said she didn't understand the question and after a brief exchange, said, "I heard my son screaming."

O'Mara got Trayvon's older brother, Jahvaris Fulton, to concede that he told a reporter that he initially wasn't sure that Trayvon was screaming on the call. Jahvaris Fulton said he'd been in a "cloud of denial" and had hoped it wasn't his brother's voice before deciding that it was. He said he has listened to the tape about 10 times.

The screams arguably are the most penetrating evidence in the case, but the voice hasn't been identified with technological certainty. The judge barred expert testimony about the voice's identity. Zimmerman has told police he screamed for help as Trayvon slammed his head against the concrete. But when investigators played the screams for him, Zimmerman said the voice "doesn't even sound like me."

After the state rested, the defense opened its case by calling Zimmerman's mother and uncle to counter the testimony of Trayvon's relatives.

"Whose voice was it?" O'Mara asked Gladys Zimmerman, after playing the 911 call.

Zimmerman's uncle, Jorge Meza, said he heard the screams on a television news report and immediately recognized the voice. "I not only heard the scream, I felt the scream in my heart," Meza said, "like my nephew is screaming for his life. It's a moment that lives with me."

Zimmerman fought back tears as he looked on from the defendant's table, in a rare expression of emotion for him during the trial.

Their testimony appeared to be a clear attempt to cancel out the emotional impact of the Fultons' testimony. Both sets of testimony being heard on the same day prevented jurors from having at least one night to absorb only the statements of Trayvon's relatives, as prosecutors had hoped.

"I'm happy the way it worked out," O'Mara told reporters after court recessed. He said he called Zimmerman's mother and uncle first because "I wanted to get out of the way that everyone in George's family knows it's his voice."

Earlier, the state concluded its case on the testimony of medical examiner Dr. Shipping Bao, who performed the autopsy of Trayvon's body. Bao spent most of the afternoon on the stand, sometimes helping and at other moments possibly hurting the state.

Bao said there were small abrasions on two of the fingers on the teen's left hand. Because Trayvon was right-handed, the state is expected to note later that the absence of similar injuries on the right hand casts doubt on Zimmerman's claim that the teen punched him 25 to 30 times.

Bao said he has "no opinion, zero" on what Zimmerman's and Trayvon's body positions were when the shot was fired. Zimmerman says he got on top of Trayvon and spread his arms apart after shooting him. But witnesses and police say they arrived and found Trayvon's arms tucked beneath his body, which was lying face down.

Bao said Trayvon probably lived for up to 10 minutes after Zimmerman's bullet cut through his heart. "He was still alive, he was still in pain," he said.

He set off a red flag for defense attorneys because Bao had changed his opinion. He initially thought Trayvon lived for no longer than three minutes after the shooting, but lengthened the estimate based on a more recent autopsy involving a similar fatal wound, he said.

Bao also changed his opinion on another critical finding regarding the THC, the active ingredient in marijuana, found in Trayvon's system. Bao at first said the amount of THC was too small to have influenced Trayvon's behavior on the night of the shooting. He said he revised his opinion, believing it could have affected the teen, after consulting experts.

On cross-examination by the defense, Bao repeatedly said he had no memory of performing the autopsy: "I do not remember anything, zero … I depend on my notes."

As Bao appeared to read from his notes as if they were a script, defense attorney Don West asked to see them. Bao refused until the judge ordered him to comply.

Bao frequently expressed hostility during West's questioning and sometimes toward the state's questions. The judge repeatedly ordered Bao not to interrupt the attorneys.

At one point, as West grilled Bao, Bao said, "Nobody knows more about Trayvon Martin's autopsy than me." West shot back, "Except you don't remember anything about the autopsy?" Bao replied, "Yes, without my notes."

Asked his opinion of how the state tried its case, O'Mara told reporters the effort was "a bit abbreviated." He said he expected more of Trayvon's relatives and police to testify. "I wasn't surprised with what they put on. I was probably more surprised by what they didn't put on."

In Court on Monday

Team Zimmerman will continue to put on its case but not likely for as long as the state did. Why? Because the defense has comparatively far less work to do to -- and already may have done enough. O'Mara on Friday said he expects to wrap up after just a few days.

Corey Dade, an award-winning journalist based in Washington, D.C., is a former national correspondent at NPR and political reporter at the Wall Street Journal, the Boston Globe and other news organizations. Follow him onTwitter.